Making an API Request

This section describes the structure of a REST API request. The API in Getting a List of RAM Managed Permissions is taken as an example to demonstrate how to call an API.

Request URI

A request URI is in the following format:

{URI-scheme} :// {Endpoint} / {resource-path} ? {query-string}

**Table 1** Parameter description
Parameter	Description
URI-scheme	Protocol used to transmit requests. All APIs use HTTPS.
Endpoint	Domain name or IP address of the server bearing the REST service. The endpoint varies between services in different regions. It can be obtained from Regions and Endpoints. For example, the endpoint of RAM is ram.myhuaweicloud.com.
resource-path	Access path of an API for performing the specified operation. You can obtain the path from the URI of an API. For example, the resource-path of the API used to list RAM managed permissions for the specified resource type is /v1/permissions.
query-string	An optional query parameter. Ensure that a question mark (?) is included before each query parameter that is in the format of Parameter name = Parameter value. For example, ?limit=10 indicates that a maximum of 10 data records will be queried.

For example, to list RAM managed permissions for the specified resource type, obtain the endpoint of RAM (ram.myhuaweicloud.com) and the resource-path (/v1/permissions) in Getting a List of RAM Managed Permissions. Then, construct the URI as follows:

Request Methods

The HTTP protocol defines the following request methods that can be used to send a request to the server.

**Table 2** REST request methods supported by RAM
Method	Description
GET	Requests the server to return specified resources.
PUT	Requests the server to update specified resources.
POST	Requests the server to add resources or perform special operations.
DELETE	Requests the server to delete specified resources.

Request Header

You can also add additional header fields to a request, such as the fields required by a specified URI or HTTP method. For example, to request for the authentication information, add Content-Type, which specifies the request body type. Table 3 describes common request headers.

The following headers need to be added to the request:

**Table 3** Common request headers
Header	Description	Mandatory
Authorization	Signature information in the request. For details about AK/SK authentication, see AK/SK Authentication. Type: string Default value: none	Yes
Content-Type	Content type, for example, application/json. Type: string Default value: none	Yes
X-Sdk-Date	Date and time when the request was sent, for example, 20221107T020014Z. Type: string Default value: none	Yes
Host	Host address, for example, ram.myhuaweicloud.com. Type: string Default value: none	Yes

APIs support AK/SK authentication, which uses SDKs to sign a request. During the signature, the Authorization (signature information) and X-Sdk-Date (time when the request is sent) headers are automatically added in the request. For details about AK/SK authentication, see AK/SK Authentication.

For the API in Getting a List of RAM Managed Permissions, the request is as follows:

GET https://ram.myhuaweicloud.com/v1/permissions 
content-type: application/json
X-Sdk-Date: 20230330T021902Z 
host: ram.myhuaweicloud.com 
Authorization: SDK-HMAC-SHA256 Access=xxxxxxxxxxxxxxxxxxx, SignedHeaders=content-type;host;x-sdk-date, Signature=xxxxxxxxxxxxxxxxxxxx

(Optional) Request Body

The body of a request is often sent in a structured format (JSON or XML) as specified in the Content-type header field. The request body transfers content except the request header.

The request body varies between APIs. Some APIs do not require the request body, such as the APIs requested using the GET and DELETE methods.